A facile synthesis of homotriptycenes from anthranol derivatives

Substituted trans-10-benzyl-9-anthranols 5a,b and substituted 10,10-dibenzyl-9-anthranol 8e undergo intramolecular cyclization in the presence of formic or oxalic acid to give homotriptycenes 9a,b,e. Depending on the amount of acid used, a competitive 1,4-dehydration to anthracene derivatives 10a,b was observed for 5a,b. The latter process was the only reaction pathway for anthranols that do not possess electron-donating substituents on benzyl moiety (5c,d -> 10c,d).